Climate Change HEALTH

Posts Tagged ‘coral’

Ocean acidification has emerged as an extreme threat to marine ecosystems and fisheries – it may be the real threat from climate change, ready to blind-side us in just a few decades.

Why do I say that?

Our oceans have absorbed around one-third of the CO2 emitted so far. This (along with heat-absorption from the atmosphere) has had a moderating effect on temperature increases measured so far – climate change to date could have been worse than it is.

An unexpected problem has emerged, however.

When carbon dioxide dissolves in seawater it forms a weak acid (carbonic acid) – as CO2 has accumulated in oceans around the world, they have slowly but surely become more acidic (so far about one-tenth of one pH unit). Although the increase in acidity to date doesn’t seem like much, it is already having measurable biological and physical effects.

The main issue relates to the hardening (or calcification) of marine shells. Shell-forming organisms need a fairly narrow pH range to allow them to get calcium out of solution in seawater and deposit it in their shells.

But as the water becomes more acidic, shell calcification decreases, and at some point actually begins to reverse, causing shells and related structures (like coral reefs) to start dissolving – one study estimates that ALL coral reefs may cease to grow and start to dissolve when atmospheric CO2 reaches 560ppm. It is also likely that most regions will be inhospitable to coral reefs by 2050 (including Australia’s Great Barrier Reef).

This issue does not just affect oceans.

It affects all of us because it will cause major changes to marine food chains.

And if ocean ecosystems collapse, what happens to us?

Ocean acidification due to climate change

Further Reading

Acid In The Oceans: A Growing Threat To Sea Life

Can Corals Survive In A Warming World?

An ocean of poison

Report Warns about Carbon Dioxide Threats to Marine Life – download a PDF of “Impacts of Ocean Acidification on Coral Reefs and Other Marine Calcifiers.”

Ocean acidification: the other CO₂ problem

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According to an online report from The Sydney Morning Herald, climate change-related damage to Australia’s Great Barrier Reef will cost us some $37.5 billion during this century.

If greenhouse gas emissions are not reduced globally, the Great Barrier Reef is expected to be one of the first of Australia’s World Heritage sites seriously damaged. But chairman of the Great Barrier Reef Foundation Dr John Schubert warned that with climate change happening much faster than predicted, Australia must plan to ”adapt” the reef to save it from some level of damage scientists say is inevitable.

According to the article:

”There needs to be extra emphasis on the adaptation side,” said Dr Schubert, who is also the outgoing chairman of the Commonwealth Bank and sits on the board of BHP-Billiton and Qantas. He said the report by Oxford Economics was a conservative assessment of the losses if the reef was damaged by permanent bleaching.

Anemone Fish - Great Barrier Reef

Bleaching (due to higher water temperatures) is not the only threat facing coral reefs. With atmospheric CO2 levels rising fast, ocean acidification is fast becoming THE major threat to all marine ecosystems.

The oceans absorb a lot of the CO2 emitted by human activities. When it dissolves in seawater it forms carbonic acid – this makes the oceans more acidic.

Shell-forming sea creatures (including coral polyps) can only deposit calcium in their shells when pH is between a certain critical range (see diagram).And if they can’t harden their shells they can’t survive, or form coral reefs for that matter.

As the oceans become more acidic, it is likely that large areas will become less hospitable to marine life – this will damage ocean food webs significantly as many crustaceans (and related species) are food for fish and other animals higher up the food chain.

More about ocen acidification coming soon…

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